U.S. patent application number 13/794856 was filed with the patent office on 2013-08-15 for method and apparatus for bending long member, and method for bending door frame.
This patent application is currently assigned to SHIROKI CORPORATION. The applicant listed for this patent is SHIROKI CORPORATION. Invention is credited to Akinori MATUBARA, Yuji MORI, Kazuyuki TAKAGI, Jiro YOSHIHARA.
Application Number | 20130205912 13/794856 |
Document ID | / |
Family ID | 45938170 |
Filed Date | 2013-08-15 |
United States Patent
Application |
20130205912 |
Kind Code |
A1 |
YOSHIHARA; Jiro ; et
al. |
August 15, 2013 |
METHOD AND APPARATUS FOR BENDING LONG MEMBER, AND METHOD FOR
BENDING DOOR FRAME
Abstract
A method of bending a long member includes applying a tensile
force to the long member to draw out the long member in a
lengthwise direction thereof, measuring a displacement of the long
member after commencement of the application of the initial tensile
force, and bending the long member by applying a correction tensile
force and a bending pressure for bending the long member into a
curved shape in the lengthwise direction simultaneously to the long
member upon the displacement exceeding a predetermined tensile
fracture threshold value within a predetermined period of time or
after a lapse of the predetermined period of time without the
displacement exceeding the tensile fracture threshold value. The
correction tensile force is smaller than the tensile force at the
time the displacement exceeds the tensile fracture threshold value
or the tensile force at the lapse of the predetermined period of
time.
Inventors: |
YOSHIHARA; Jiro; (Kanagawa,
JP) ; TAKAGI; Kazuyuki; (Kanagawa, JP) ;
MATUBARA; Akinori; (Kanagawa, JP) ; MORI; Yuji;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIROKI CORPORATION; |
|
|
US |
|
|
Assignee: |
SHIROKI CORPORATION
Kanagawa
JP
|
Family ID: |
45938170 |
Appl. No.: |
13/794856 |
Filed: |
March 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2011/070927 |
Sep 14, 2011 |
|
|
|
13794856 |
|
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Current U.S.
Class: |
73/834 |
Current CPC
Class: |
B21D 7/00 20130101; B21D
25/02 20130101; G01N 3/08 20130101; B21D 7/14 20130101 |
Class at
Publication: |
73/834 |
International
Class: |
G01N 3/08 20060101
G01N003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2010 |
JP |
2010-230502 |
Claims
1. A method of bending a long member, comprising: applying a
tensile force, which increases from an initial tensile force, to
said long member to draw out said long member in a lengthwise
direction thereof; measuring a displacement of said long member
after commencement of said application of said initial tensile
force; and bending said long member by applying a correction
tensile force and a bending pressure for bending said long member
into a curved shape in said lengthwise direction simultaneously to
said long member upon said displacement exceeding a predetermined
tensile fracture threshold value within a predetermined period of
time or after a lapse of said predetermined period of time without
said displacement exceeding said tensile fracture threshold value,
wherein said correction tensile force is smaller than said tensile
force at the time said displacement exceeds said tensile fracture
threshold value or said tensile force at said lapse of said
predetermined period of time.
2. The long-member bending method according to claim 1, wherein,
during said bending, upon said displacement of said long member
after the commencement of the application of said initial tensile
force exceeding said predetermined tensile fracture threshold value
within said predetermined period of time, a plurality of correction
tensile force values are selectively set in accordance with a time
taken until said displacement exceeds said tensile fracture
threshold value.
3. The long-member bending method according to claim 1, wherein,
during said bending, upon said predetermined period of time
elapsing without said displacement of said long member, after said
commencement of said application of said initial tensile force,
exceeding said tensile fracture threshold value, a plurality of
correction tensile force values are selectively set in accordance
with the amount of displacement of said long member at said lapse
of said predetermined period of time.
4. An apparatus for bending a long member, comprising: a bender
which applies a variable tensile force for drawing out said long
member in a lengthwise direction thereof and a bending pressure for
bending said long member into a curved shape in said lengthwise
direction to said long member; a displacement measurer which
measures, when said variable tensile force which increases from an
initial tensile force is applied to said long member by said
bender, a displacement of said long member caused by said variable
tensile force; and a controller which commands, when said
displacement of said long member that is measured by said
displacement measurer exceeds a tensile fracture threshold value
within a predetermined period of time or said predetermined period
of time elapses without said displacement of said long member that
is measured by said displacement measurer exceeding said tensile
fracture threshold value, said bender to apply said bending
pressure to said long member after changing said variable tensile
force of said bender to a correction tensile force which is smaller
than the variable tensile force at the time said displacement
exceeds said tensile fracture threshold value or a correction
tensile force which is smaller than the variable tensile force at
said lapse of said predetermined period of time.
5. A method of bending a door frame, comprising: applying a tensile
force which increases from an initial tensile force to said door
frame to draw out said door frame in a lengthwise direction
thereof; measuring a displacement of said door frame after
commencement of said application of said initial tensile force; and
bending said door frame by applying a correction tensile force and
a bending pressure for bending said door frame into a curved shape
in said lengthwise direction simultaneously to said door frame upon
said displacement exceeding a predetermined tensile fracture
threshold value within a predetermined period of time or after a
lapse of said predetermined period of time without said
displacement exceeding said tensile fracture threshold value,
wherein said correction tensile force is smaller than said tensile
force at the time said displacement exceeds said tensile fracture
threshold value or said tensile force at said lapse of said
predetermined period of time.
Description
RELATED APPLICATION DATA
[0001] This is a continuation of International Application No.
PCT/JP2011/070927, with an international filing date of Sep. 14,
2011, which is herein incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method and apparatus for
bending a long member made of aluminum, iron or the like to
produce, e.g., a vehicle door frame.
BACKGROUND ART
[0003] FIG. 6 is a flowchart showing a conventional process of
bending a long member. First, a tensile force is applied to a long
member in a single uniform manner for a predetermined period of
time to draw out the long member in the lengthwise direction (S1,
S2: YES), and a bending pressure is applied to the long member to
bend the long member into a curved shape in the lengthwise
direction thereof after the tensile force is reduced in accordance
with the drawn-out amount of the long member (S3, S4, S5).
CITATION LIST
Patent Literature
[0004] Non-Patent literature 1: Journal of Technical Disclosure No.
2005-505666 in Journal of technical disclosure of Japan Institute
of Invention and Innovation
[0005] However, in the aforementioned prior art, since a tensile
force is applied to long members in a single uniform manner for a
predetermined period of time, if the long members are low in
tensile strength, it is often the case that the long members cannot
acceptably pass as a commodity product as a result of
cross-sectional distortion, deformation or rupture (tensile
fracture) caused by an excessive elastic fracture or permanent
deformation occurring upon a lapse of the predetermined period of
time. As shown in FIG. 7, the tensile strength of each long member
is proportional to the hardness of the material thereof as a
general rule; however, due to slight difference in length and
sectional area caused by weight reduction and wall-thickness
reduction in recent years, the value of tensile strength varies
widely for different long members even if the materials thereof
have the same hardness in a lot that is identical in name and in
notation. In addition, even in the case of long members of the same
material, long members made of aluminum, which have come to be
referred to as "seasonal products", particularly vary widely in
tensile strength depending on the season, temperature and humidity.
FIG. 8 shows variations in tensile strength of aluminum-made
products of the same lot. Accordingly, in the above described
conventional art, it has been difficult to perform a favorable
bending process on long members which vary widely in tensile
strength, especially long members which are low in tensile
strength.
[0006] The present invention has been devised based on the
awareness of the above-mentioned issues, and an object of the
present invention is to obtain a long-member bending method and
apparatus, and a door frame bending method, each of which makes it
possible to perform a favorable bending process on long members
which vary widely in tensile strength, especially long members
which are low in tensile strength.
SUMMARY OF THE INVENTION
[0007] The present invention has been accomplished based on the
finding that, upon revising the conventional technical common
knowledge of a tensile force being applied to long members (door
frames) in a single uniform manner for a predetermined period of
time, it is possible to perform a favorable bending process even on
a long member which is low in tensile strength without causing
tensile fracture if the displacement from the commencement of the
application of an initial tensile pressure is measured (monitored)
on each long member and if, upon the displacement of a long member
exceeding a predetermined tensile fracture threshold value within a
predetermined period of time or after a lapse of this predetermined
period of time without the displacement of the long member
exceeding this predetermined tensile fracture threshold value, a
correction tensile force which is smaller than the tensile force at
that time is immediately set and thereupon a bending process is
performed by applying this correction tensile force and a bending
pressure to the long member so that the lengthwise direction
thereof becomes curved.
[0008] Namely, a long-member bending method according to the
present invention is characterized by including a applying a
tensile force, which increases from an initial tensile force, to
the long member to draw out the long member in a lengthwise
direction thereof; measuring a displacement of the long member
after commencement of the application of the initial tensile force;
and a bending the long member by applying a correction tensile
force and a bending pressure for bending the long member into a
curved shape in the lengthwise direction simultaneously to the long
member upon the displacement exceeding a predetermined tensile
fracture threshold value within a predetermined period of time or
after a lapse of the predetermined period of time without the
displacement exceeding the tensile fracture threshold value,
wherein the correction tensile force is smaller than the tensile
force at the time the displacement exceeds the tensile fracture
threshold value or the tensile force at the lapse of the
predetermined period of time.
[0009] In the present specification, "tensile fracture" refers to
the phenomenon of a defect, such as cross-sectional distortion,
deformation or a rupture caused by an excessive elastic fracture or
permanent deformation, occurring in a long member when this long
member is drawn out in the lengthwise direction for a long period
of time so that this long member cannot acceptably pass as a
commodity product.
[0010] In the present specification, "tensile fracture threshold
value" refers to a displacement which may cause tensile fracture if
a long member is further drawn out when it is drawn out in the
lengthwise direction by an application of a tensile force to the
long member (or a displacement slightly smaller than such a
displacement). Namely, no tensile fracture has yet occurred at the
moment the displacement of the long member exceeds the tensile
fracture threshold value, so that tensile fracture can be reliably
prevented from occurring if, immediately after the displacement of
the long member exceeds the predetermined tensile fracture
threshold value, the tensile force applied to the long member is
changed to a correction tensile force which is smaller than the
tensile force at that time.
[0011] During the bending, upon the displacement of the long member
after the commencement of the application of the initial tensile
force exceeding the predetermined tensile fracture threshold value
within the predetermined period of time, it is desirable for a
plurality of correction tensile force values to be selectively set
in accordance with a time taken until the displacement exceeds the
tensile fracture threshold value.
[0012] This makes it possible to set an optimum correction tensile
force to perform a favorable bending process on each long member
which is low in tensile strength and in which tensile fracture may
occur.
[0013] During the bending, upon the predetermined period of time
elapsing without the displacement of the long member, after the
commencement of the application of the initial tensile force,
exceeding the tensile fracture threshold value, it is desirable for
a plurality of correction tensile force values are selectively set
in accordance with the amount of displacement of the long member at
the lapse of the predetermined period of time.
[0014] This makes it possible to set an optimum correction tensile
force to perform a favorable bending process on each long member
which has a degree of tensile strength such a tensile fracture
cannot occur.
[0015] The present invention is characterized by an apparatus for
bending a long member, including a bender which applies a variable
tensile force for drawing out the long member in a lengthwise
direction thereof and a bending pressure for bending the long
member into a curved shape in the lengthwise direction to the long
member; a displacement measurer which measures, when the variable
tensile force which increases from an initial tensile force is
applied to the long member by the bender, a displacement of the
long member caused by the variable tensile force; and a controller
which commands, when the displacement of the long member that is
measured by the displacement measurer exceeds a tensile fracture
threshold value within a predetermined period of time or the
predetermined period of time elapses without the displacement of
the long member that is measured by the displacement measurer
exceeding the tensile fracture threshold value, the bender to apply
the bending pressure to the long member after changing the variable
tensile force of the bender to a correction tensile force which is
smaller than the variable tensile force at the time the
displacement exceeds the tensile fracture threshold value or a
correction tensile force which is smaller than the variable tensile
force at the lapse of the predetermined period of time.
[0016] The present invention is characterized by a method of
bending a door frame, including applying a tensile force which
increases from an initial tensile force to the door frame to draw
out the door frame in a lengthwise direction thereof; measuring a
displacement of the door frame after commencement of the
application of the initial tensile force; and bending the door
frame by applying a correction tensile force and a bending pressure
for bending the door frame into a curved shape in the lengthwise
direction simultaneously to the door frame upon the displacement
exceeding a predetermined tensile fracture threshold value within a
predetermined period of time or after a lapse of the predetermined
period of time without the displacement exceeding the tensile
fracture threshold value, wherein the correction tensile force is
smaller than the tensile force at the time the displacement exceeds
the tensile fracture threshold value or the tensile force at the
lapse of the predetermined period of time.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0017] According to the prevent invention, a long-member bending
method and apparatus, and a door frame bending method, each of
which makes it possible to perform a favorable bending process on
long members which vary widely in tensile strength, especially long
members which are low in tensile strength, can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a diagram showing the configuration of a
long-member bending apparatus, according to the present
invention;
[0019] FIGS. 2A and 2B are charts showing examples of data stored
in a correction tensile force holding table;
[0020] FIG. 3 is a flow chart showing a long-member bending process
according to the present invention;
[0021] FIG. 4 is a diagram showing the difference in displacement
between long members which are mutually different in hardness
(tensile strength);
[0022] FIG. 5 is a diagram showing the control of tensile force
applied to long members which vary widely in tensile strength;
[0023] FIG. 6 is a flow chart showing a conventional long-member
bending process;
[0024] FIG. 7 is a diagram showing the general relationship between
tensile strength and material hardness; and
[0025] FIG. 8 is a diagram showing a dispersion of the tensile
strength values of long members made of aluminum.
DESCRIPTION OF THE EMBODIMENT
[0026] An embodiment in which a long-member (door-frame) bending
apparatus 1 according to the present invention has been applied to
a vehicle door frame production will be hereinafter discussed with
reference to FIGS. 1 through 5. The long-member bending apparatus 1
is provided with benders (bending devices) 10 which applies, to a
long member (door frame) W made of aluminum or iron, a variable
tensile force for drawing out the long member W in the lengthwise
direction, and a bending pressure for bending the long member W
into a curved shape in the lengthwise direction. The benders 10 are
respectively provided with chucks 11 which hold both ends of the
long member W to fix the long member W, a cylinder not shown in the
drawings is fixed to the chucks 11, and a variable tensile force is
applied to the long member W in the lengthwise direction by
applying a tensile force to the chucks 11 via the aforementioned
cylinder. In addition, the chucks 11 are supported by a swingable
support not shown in the drawings, and a bending pressure for
bending the long member W into a curved shape in the lengthwise
direction thereof is applied to the long member W by pressing the
long member W against a metallic mold 12 while swinging the
swingable support.
[0027] The bending apparatus 1 is provided with a displacement
measurer 20 which measures a displacement d of the long member W
when a tensile force is applied to the long member W, both ends of
which are held by the chucks 11. The displacement measurer 20 can
be, e.g., an encoder (not shown) which measures the displacement d
of the long member W by converting the displacement d into a pulse
number, or a system which measures the displacement d of the long
member W by converting the amount of pressing a press member (not
shown) pressed by the chucks 11, to which a tensile force is given
into the displacement d of the long member W. Namely, the
displacement measurer 20 can be of any type as long as it can
measure the displacement d of the long member W.
[0028] The bending apparatus 1 is provided with a controller 30
which inputs the displacement d of the long member W, which is
measured by the displacement measurer 20, to control via the
benders 10 the variable tensile force applied to the long member
W.
[0029] More specifically, the controller 30 sends a signal to the
benders 10 commanding the benders 10 to apply a variable tensile
force, to the long member W, which slowly increases from an initial
tensile force; subsequently, the controller 30 commences to count
time via a timer 40. Upon the displacement d of the long member W
that is input from the displacement measurer 20 exceeding a tensile
fracture threshold value D within a predetermined period of time,
the controller 30 sends a signal to the benders 10 commanding the
benders 10 to change the variable tensile force applied to the long
member W to a correction tensile force which is smaller than the
tensile force at the time the displacement d exceeds the tensile
fracture threshold value D. Upon the predetermined period of time
elapsing without the displacement d of the long member W that is
input from the displacement measurer 20 exceeding the tensile
fracture threshold value D, the controller 30 sends a signal to the
benders 10 commanding the benders 10 to change the variable tensile
force applied to the long member W to a correction tensile force
which is smaller than the tensile force at the lapse of the
predetermined period of time.
[0030] "Tensile fracture" herein refers to a phenomenon in which a
defect such as cross-sectional distortion, deformation or rupture
that is caused by an excessive elastic fracture or permanent
deformation occurs in the long member W when the long member W is
drawn out in the lengthwise direction for a long period of time,
and in which the long member W no longer can acceptably pass as a
commodity product. In addition, "tensile fracture threshold value
D" refers to a displacement which may cause tensile fracture if the
long member W is further drawn out when it is drawn out in the
lengthwise direction by an application of a tensile force to the
long member W (or a displacement slightly smaller than such a
displacement). Namely, no tensile fracture has yet occurred at the
moment the displacement of the long member W exceeds the tensile
fracture threshold value D, so that tensile fracture can be
reliably prevented from occurring if, immediately after the
displacement of the long member W exceeds the tensile fracture
threshold value D, the tensile force applied to the long member W
is changed to a correction tensile force which is smaller than the
tensile force at that time.
[0031] The controller 30 is connected to a correction tensile force
holding table 50, in which a plurality of correction tensile force
values for providing instructions to the benders 10 are stored to
be capable of being selectively set. FIG. 2 shows an example of
data stored in the correction tensile force holding table 50. The
data shown in FIG. 2A shows the correlation between the time taken
until the displacement d of the long member W exceeds the tensile
fracture threshold value D when the displacement d of the long
member W that is input from the displacement measurer 20 exceeds
the tensile fracture threshold value D within a predetermined
period of time and a plurality of correction tensile force values.
The data shown in FIG. 2B shows the correlation between the
displacement d of the long member W at a lapse of the predetermined
period of time when the predetermined period of time elapses
without the displacement d of the long member W that is input from
the displacement measurer 20 exceeding the tensile fracture
threshold value D and a plurality of correction tensile force
values. In this connection, the correction tensile force holding
table 50 can be stored in an internal memory of the bending
apparatus 1 or an external memory which is connected to the
controller 30.
[0032] Operations of the bending apparatus 1 that has been
structured as above will be hereinafter discussed in detail with
reference to the flow chart shown in FIG. 3. First, with both ends
of the long member W held and fixed by the chucks 11 of the benders
10, the controller 30 sends a signal to the benders 10 commanding
the benders 10 to apply a variable tensile force to the long member
W which slowly increases from an initial tensile force, and
subsequently, the controller 30 commences to count time via the
timer 40. The benders 10 which have received the command signal
from the controller 30 commence to apply a variable tensile force
for drawing out the long member W in the lengthwise direction to
the long member W by applying a tensile force to the chucks 11 via
the cylinder not shown in the drawings (S1). Simultaneously, the
displacement measurer 20 commences to measure the displacement d of
the long member W at this application of the variable tensile force
and inputs the result of this measurement to the controller 30.
[0033] Upon determining that the displacement d of the long member
W that is input from the displacement measurer 20 has exceeded the
tensile fracture threshold value D within a predetermined period of
time (S2: YES), the controller 30 checks the time taken until the
displacement d exceeds the tensile fracture threshold value D (S3),
and the controller 30 refers to the correction tensile force
holding table 50 and sets a correction tensile force value
corresponding to the time until the displacement d exceeds the
tensile fracture threshold value D (S4). For instance, in FIG. 2A,
if the time taken until the displacement d exceeds the tensile
fracture threshold value D is within time T1, T2 or T3, the
controller 30 sets the value of the correction tensile force to A,
B or C, respectively. Subsequently, the controller 30 sends a
signal to the benders 10 commanding the benders 10 to change the
variable tensile force applied to the long member W to the set
correction tensile force. Lastly, a bending operation is performed
to bend the long member W into a curved shape in the lengthwise
direction by pressing the long member W against the metallic mold
12 while swinging the swingable support not shown in the drawings
that supports each chuck 11 (S5).
[0034] On the other hand, upon detecting that the predetermined
period of time has elapsed without the displacement d of the long
member W that is input from the displacement measurer 20 exceeding
the tensile fracture threshold value D (S2: No, S6: Yes), the
controller 30 checks the displacement d at the lapse of the
predetermined period of time (S7), refers to the correction tensile
force holding table 50, and sets a correction tensile force value
corresponding to the displacement d of the long member W at the
lapse of the predetermined period of time (S8). For instance, in
FIG. 2B, if the displacement d of the long member W at the lapse of
the predetermined period of time is within displacement d1, d2 or
d3, the controller 30 sets the value of the correction tensile
force to X, Y or Z, respectively. Subsequently, the controller 30
sends a signal to the benders 10 commanding the benders 10 to
change the variable tensile force applied to the long member W to
the set correction tensile force. Lastly, a bending operation is
performed to bend the long member W into a curved shape in the
lengthwise direction by pressing the long member W against the
metallic mold 12 while swinging the swingable support, not shown in
the drawings, that supports each chuck 11 (S9).
[0035] Assuming that the tensile strength of the long member W is
associated with the hardness of the material thereof, the
displacement d of the long member W becomes smaller as the material
of the long member W becomes greater in hardness, while the
displacement d of the long member W becomes greater as the material
of the long member W becomes smaller in hardness. Accordingly, if a
tensile force continues to be applied in a single uniform manner to
all long members W, which vary widely in tensile strength, for a
predetermined period of time, the displacement d at the lapse of
the predetermined period of time exceeds the tensile fracture
threshold value D in some long members W (range I), while in other
long members W (range II), the displacement d at the lapse of the
predetermined period of time does not exceed the tensile fracture
threshold value D. Although the long members W in range II cause no
problems with tensile fracturing, there is a high possibility of
the long members W in range I having already caused a tensile
fracture at the lapse of the predetermined period of time.
[0036] Accordingly, for the long member W in range I, immediately
after the displacement d exceeds the tensile fracture threshold
value D, the tensile force applied to the long member W is changed
to a correction tensile force which is smaller than the tensile
force at the time the displacement d exceeds the tensile fracture
threshold value D to prevent a tensile fracture from occurring in
the long member W as shown by a solid line in FIG. 5 (S2 through S5
in the flow chart shown in FIG. 3). In addition, for the long
member W in range II, the displacement d does not exceed the
tensile fracture threshold value D even after the lapse of the
predetermined period of time, and after this lapse of the
predetermined period of time, the tensile force applied to the long
member W is changed to a correction tensile force which is smaller
than the tensile force at that time, and accordingly, no tensile
fracture occurs in the long member W (S2, S6 through S9 in the flow
chart shown in FIG. 3).
[0037] As described above, according to the present embodiment of
the long-member bending method, this method includes: a step of
applying a tensile force which increases from an initial tensile
force to the long member W to draw out the long member W in the
lengthwise direction; a step of measuring the displacement d of the
long member W after the commencement of the application of the
initial tensile force; and a step of bending the long member W by
applying a correction tensile force and a bending pressure for
bending the long member W into a curved shape in the lengthwise
direction to the long member W simultaneously, upon the
displacement d exceeding the predetermined tensile fracture
threshold value D within a predetermined period of time or after a
lapse of the predetermined period of time without the displacement
d exceeding the tensile fracture threshold value D, wherein the
aforementioned correction tensile force is smaller than the tensile
force at the time the displacement d exceeds the tensile fracture
threshold value D or the tensile force at the lapse of the
predetermined period of time; accordingly, a favorable bending
process can be performed on long members W which vary widely in
tensile strength, especially long members W which are low in
tensile strength.
INDUSTRIAL APPLICABILITY
[0038] A long-member bending method and apparatus, and a door frame
bending method according to the present invention are suitable for
use as a method and apparatus for bending a long member made of
aluminum, iron or the like to produce, e.g., a vehicle door frame
and a method of bending a door frame.
DESCRIPTION OF THE REFERENCE NUMERALS
[0039] 1 Long-member bending apparatus
[0040] 10 Bender (bending device)
[0041] 11 Chuck
[0042] 12 Metallic mold
[0043] 20 Displacement measurer
[0044] 30 Controller
[0045] 40 Timer
[0046] 50 Correction tensile force holding table
[0047] W Long member (door frame)
[0048] d Displacement
[0049] D Tensile fracture threshold value
* * * * *